Project Summary/ Abstract: Endometriosis is a painful disorder where endometrium-like tissue forms lesions outside of the uterine cavity. The prevalent theory, the Sampson Hypothesis, is that endometrial fragments pass [retrograde] through the fallopian tube to establish the lesions. Despite recent advances in medical therapy, there remains no cure for the disease and surgical removal of the lesions remains a choice for many women. Unfortunately, the recurrence rate for endometriosis after surgery is high with patients requiring multiple operations and medical treatment. Factors contributing to recurrence include further retrograde menstruation and seeding as well as the presence of minute endometriotic residues that are missed during surgery. Intraoperative visualization of these minute lesions poses an imaging challenge for gynecologic surgeons. Our goal is to reduce recurrence of the disease after surgery. We have created and patented a nanoplatform that can be administered systemically before surgery to delineate unresected tissue with real-time near infrared (NIR) fluorescence during surgery and eliminate unresected residues with photothermal ablation. The platform was originally developed for cancer therapy and is applicable to endometriosis. The reagent consists of the NIR dye, silicon naphthalocyanine (SiNc) encapsulated in biodegradable PEG-PCL (poly (ethylene glycol)-b-poly(?- caprolactone)) nanoparticles. The particles are non-fluorescent until activated within the target cells. In preliminary studies, we assessed the NIR reagent in macaque endometriotic tissue grafted into severe combined immunodeficient (SCID) mice. We reported that our currently developed nanoparticles internalized in macaque endometriotic cells and generated a NIR fluorescence signal in lesions in the mice. The NIR treatment also ablated the endometriotic grafts. Our premise is that nanoparticle platform-assisted surgical techniques can be employed clinically to permit intraoperative visualization and elimination of the unresected endometriosis. In this grant, we propose that the specificity of our existing platform can be enhanced by targeting cell surface receptors in endometriotic lesions. This refinement is an essential step towards creating new surgical techniques, assessing the safety of the procedures, and conducting impactful future experiments. In specific aim 1, we will synthesize polymeric nanoparticles that target VEGF receptor 2 (KDR), or other cell surface moieties, overexpressed in endometriosis; assess the particles in human cells and compare the reagent to our current platform in macaque tissue. In specific aim 2 we will validate that the new targeted agent can be injected systemically and then specifically accumulate in human lesions engrafted into SCID mice, and that targeted NIR treatment results in photothermal ablation of the xenografts. Old-World nonhuman primates, including macaques develop spontaneous endometriosis and provide an animal model for creating new surgical techniques. To advance this model, in specific aim 3 we will extend our studies to test nanoparticle-based ablation of ectopic endometrium in macaques.